Ethylene propylene rubber conductive coating, preparation method thereof and cable accessory

Abstract

The invention discloses an ethylene propylene rubber conductive coating, the ethylene propylene rubber conductive coating is not vulcanized in a preparation process, a heating vulcanization process is performed after coating, and the ethylene propylene rubber conductive coating is prepared from the following raw materials in parts by mass: 100 parts of ethylene propylene rubber, 1-3 parts of a heat-resistant agent, 80-150 parts of a plasticizer, 5-20 parts of a tackifier, 80-120 parts of conductive carbon black and 1-3 parts of a vulcanizing agent. 2-4 parts of an accelerant and 150-300 parts of a dispersing solvent. According to the invention, ethylene propylene rubber is adopted as a main body material, and conductive carbon black is added, so that the coating has excellent conductivity and shielding performance, can be used for replacing an existing conductive shielding layer needing to be prefabricated, does not need special forming equipment, and is simple in manufacturing process and low in cost; the ethylene propylene rubber conductive coating does not need to be vulcanized in the preparation process, and is heated and vulcanized after being coated on the surface of an object, so that the adhesive force of a coating finished product is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive coatings, and particularly to an ethylene-propylene rubber conductive coating, a preparation method thereof, and a cable accessory. Background Art

[0002] At present, ethylene-propylene rubber is widely used in the cable accessory industry. In order to protect the insulating layer of the cable accessory from damage caused by electric field stress concentration and to suppress induced charges, a conductive shielding layer needs to be wrapped outside the insulating layer. However, this conductive shielding layer is generally vulcanized and formed in a mold in combination with insulating rubber. The manufacturing process is relatively complex, requiring the production of special molds, special equipment for forming, and the adjustment of the forming process. Sometimes, there may be poor adhesion between the insulating rubber material and the conductive material.

[0003] In the prior art, conductive coatings are widely used and are usually coated on non-conductive substrates (such as plastics, ceramics, tempered glass, etc.) to make them conductive, so as to achieve the purpose of conduction, anti-static or electromagnetic shielding. They have the advantages of simple equipment, convenient construction, low cost, and can be coated on the surfaces of various complex shapes. However, due to the limitations of the conductive coating material, there is currently no method and process for coating a conductive coating on the outside of an ethylene-propylene rubber insulating layer to replace the conductive shielding layer.

[0004] The above content is only used to assist in understanding the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main object of the present invention is to provide an ethylene-propylene rubber conductive coating, a preparation method thereof, and a cable accessory, which use a conductive coating to replace the conductive shielding layer to play an external shielding or conductive role, and at the same time have the advantages of simple operation and low cost.

[0006] To achieve the above object, the present invention provides an ethylene-propylene rubber conductive coating. The ethylene-propylene rubber conductive coating is not vulcanized during the preparation process and is heated and vulcanized after coating. The ethylene-propylene rubber conductive coating includes the following preparation raw materials in parts by mass:

[0007] 100 parts of ethylene-propylene rubber, 1 - 3 parts of heat-resistant agent, 80 - 150 parts of plasticizer, 5 - 20 parts of tackifier, 80 - 120 parts of conductive carbon black, 1 - 3 parts of vulcanizing agent, 2 - 4 parts of accelerator, and 150 - 300 parts of dispersion solvent.

[0008] Optionally, the heat-resistant agent is nano-sized zinc oxide, the plasticizer is one or more of white naphthenic oil, transformer oil, and paraffin oil, and the tackifier is one or more of phenolic resin, petroleum resin, and coumarone resin.

[0009] Optionally, the dispersion solvent is one or more of toluene, xylene, and acetone.

[0010] Optionally, the dispersion solvent is a mixture of toluene, xylene, and acetone in a mass ratio of 1:2:1.

[0011] Optionally, the accelerator is one or more of thiuram accelerators, thiazole accelerators, and sulfenamide accelerators.

[0012] Optionally, the vulcanizing agent is sulfur; the temperature of the heat vulcanization process is 80 - 150 °C, and the heating time is 1 - 2 h.

[0013] In addition, to achieve the above object, the present invention also provides a preparation method of an ethylene - propylene rubber conductive coating. The preparation method of the ethylene - propylene rubber conductive coating is used to prepare the above - mentioned ethylene - propylene rubber conductive coating, and the preparation method of the ethylene - propylene rubber conductive coating includes the following steps:

[0014] Knead ethylene - propylene rubber and a heat - resistant agent using a kneader to obtain a first rubber compound;

[0015] Add a tackifier, a plasticizer, and conductive carbon black to the first rubber compound, and knead and mix them using a kneader to obtain a second rubber compound;

[0016] Place the second rubber compound on an open mill with a roll temperature below 40 °C, add a vulcanizing agent and an accelerator, perform thin - pass mixing until uniform, then take off the sheet and cut it into strip - shaped rubber compounds;

[0017] Cut the above - mentioned strip - shaped rubber compounds into small pieces of materials, put them into a container containing a dispersion solvent, and stir them using a high - speed stirrer to fully dissolve them. After filtration, store them in a sealed manner to obtain the ethylene - propylene rubber conductive coating.

[0018] Optionally, the stirring speed of the high - speed stirrer is 600 - 1200 rpm, and the stirring time is 60 - 120 min.

[0019] Optionally, the step of adding a tackifier, a plasticizer, and conductive carbon black to the first rubber compound and kneading and mixing them using a kneader to obtain a second rubber compound includes:

[0020] First, add all of the tackifier, the first portion of the plasticizer, and the second portion of the conductive carbon black to the first rubber compound, raise the temperature to 98 - 105 °C, and knead for 18 - 25 min;

[0021] Then add the remaining portion of the plasticizer and the third portion of the conductive carbon black, knead using a kneader for 18 - 25 min, and then add the remaining portion of the conductive carbon black and continue to knead in a sealed manner for 25 - 35 min to obtain the second rubber compound.

[0022] In addition, to achieve the above object, the present invention further provides a cable accessory, which includes an insulating layer and a coating layer coated on the outer surface of the insulating layer. The coating layer is formed by spraying or brushing with the ethylene-propylene rubber conductive coating as described in any one of claims 1 to 5.

[0023] Optionally, the thickness of the coating layer is 0.5 - 1 mm.

[0024] The beneficial effects of the present invention are as follows: Using ethylene-propylene rubber as the main material and adding conductive carbon black, the coating has excellent electrical conductivity and shielding performance, can be used to replace the existing prefabricated conductive shielding layer, does not require special forming equipment, has a simple manufacturing process and low cost; this ethylene-propylene rubber conductive coating does not need vulcanization during the preparation process, but is vulcanized by heating after being coated on the surface of an object, so that the adhesion of the coating product is enhanced. Especially when coated on the surface of an object made of the same material as the main material, such as the outer surface of the insulating layer of a cable accessory, under the action of a vulcanizing agent, a good adhesion interface material can be formed by vulcanization cross-linking between the inside of the conductive coating and the outer skin of the insulating layer, so that the ethylene-propylene rubber conductive coating has a good bonding effect, and at the same time does not affect its electrical conductivity and shielding performance, and its surface resistance is less than 5000 Ω. Description of the Drawings

[0025] Figure 1 It is a schematic flow chart of an embodiment of the preparation method of the ethylene-propylene rubber conductive coating of the present invention.

[0026] The realization, functional characteristics and advantages of the object of the present invention will be further described with reference to the embodiments and the drawings. Detailed Embodiments

[0027] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] The embodiment of the present invention provides an ethylene-propylene rubber conductive coating, which is not vulcanized during the preparation process and is vulcanized by heating after coating. Specifically, the ethylene-propylene rubber conductive coating includes the following preparation raw materials in parts by mass: 100 parts of ethylene-propylene rubber, 1 - 3 parts of heat-resistant agent, 80 - 150 parts of plasticizer, 5 - 20 parts of tackifier, 80 - 120 parts of conductive carbon black, 1 - 3 parts of vulcanizing agent, 2 - 4 parts of accelerator, and 150 - 300 parts of dispersion solvent.

[0029] The present invention uses ethylene-propylene rubber as the main material. By adding conductive carbon black, the coating has excellent electrical conductivity and shielding performance, and can be used to replace the existing prefabricated conductive shielding layer. It does not require special forming equipment, and the manufacturing process is simple and low-cost. The ethylene-propylene rubber conductive coating does not need vulcanization during the preparation process, but is vulcanized by heating after being coated on the surface of an object, and the adhesion is enhanced. Especially when coated on the surface of an object made of the same material as the main material, such as the outer surface of the insulation layer of a cable accessory, under the action of the vulcanizing agent after coating, a good adhesion interface material can be formed by vulcanization cross-linking between the inside of the conductive coating and the insulation layer outer skin, so that the ethylene-propylene rubber conductive coating has a good bonding effect, and at the same time does not affect its electrical conductivity and shielding performance, and its surface resistance is less than 5000 Ω.

[0030] Specifically, the ethylene-propylene rubber is ethylene-propylene-diene monomer rubber, which has excellent aging resistance such as heat resistance and weather resistance.

[0031] In this embodiment, the heat-resistant agent is nano-sized zinc oxide, which has small particles and a large specific surface area, and has adsorption properties. It can well promote the vulcanization and activation performance of the rubber, and can also improve the heat aging resistance of the material.

[0032] Optionally, the plasticizer is one or more of white naphthenic oil, transformer oil, and paraffin oil. By adding the plasticizer, the plasticity and fluidity of the rubber are increased, which is convenient for subsequent forming operations. In a preferred embodiment, the plasticizer consists of white naphthenic oil, transformer oil, and paraffin oil. Using them in combination can improve its forming plasticity, and paraffin oil can also improve the brightness of the material. More preferably, the composition of the plasticizer is not less than 50 parts of white naphthenic oil, not less than 40 parts of transformer oil, and not less than 20 parts of paraffin oil.

[0033] In this embodiment, the tackifier is one or more of phenolic resin, petroleum resin, and coumarone resin, which is used to improve the bonding performance of the material. In a preferred embodiment, the tackifier consists of phenolic resin, petroleum resin, and coumarone resin. More preferably, the mass ratio of phenolic resin, petroleum resin, and coumarone resin is 1:1:1. By adding the tackifier, the bonding performance of the ethylene-propylene rubber conductive coating with other materials is improved, and the tackifier and the plasticizer can act synergistically to improve the fluidity of the material.

[0034] Optionally, the dispersion solvent is one or more of toluene, xylene, and acetone. In a preferred embodiment, the dispersion solvent consists of toluene, xylene, and acetone, and toluene, xylene, and acetone are mixed according to the mass ratio of 1:2:1, and the dispersion performance is good, which can improve the stability and uniformity of the coating.

[0035] In this embodiment, the accelerator is one or more of thiuram accelerators, thiazole accelerators, and sulfenamide accelerators, which are used to form a co-vulcanization system with the vulcanizing agent to improve the vulcanization rate. Preferably, the accelerator is a mixture of accelerator TMTD (tetramethylthiuram disulfide), accelerator M (2-mercaptobenzothiazole), and accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide), and the mixing ratio can be 1:1:1.

[0036] In a preferred embodiment, the vulcanizing agent is sulfur, which does not function at room temperature and has a low cost. The ethylene-propylene rubber conductive coating provided by the present invention is subjected to a heat vulcanization process after coating. The temperature of the heat vulcanization process is 80-150°C, and the heating time is 1-2 h. In the embodiment of the present invention, the conductive coating is specifically used for brushing or spraying on the surface of the insulating layer of the cable accessory as an outer shielding layer. After coating, it is placed in an oven at a temperature of 80-150°C and heated for 1-2 h. The conductive coating undergoes a vulcanization reaction under the action of the vulcanizing agent and adheres to the outer skin of the insulating layer, serving as an external shield or a conductive connection medium, and having good adhesion at the same time.

[0037] Based on the above ethylene-propylene rubber conductive coating, a preparation method of the ethylene-propylene rubber conductive coating according to an embodiment of the present invention is proposed. Specifically, referring to Figure 1 , Figure 1 is a process schematic diagram of an embodiment of the preparation method of the ethylene-propylene rubber conductive coating of the present invention. The preparation method of the ethylene-propylene rubber conductive coating provided in this embodiment is simple and does not require a vulcanization reaction. The preparation method of the above ethylene-propylene rubber conductive coating includes the following steps:

[0038] Step S10: Knead ethylene-propylene rubber and a heat-resistant agent using a kneader to obtain a first rubber compound;

[0039] Step S20: Add a tackifier, a plasticizer, and conductive carbon black to the first rubber compound, and knead and mix them using a kneader to obtain a second rubber compound;

[0040] Step S30: Place the second rubber compound on an open mill with a roll temperature below 40°C, add a vulcanizing agent and an accelerator, mix and knead thinly and evenly, then take off the sheet and cut it into strip-shaped rubber compounds;

[0041] Step S40: Cut the above strip-shaped rubber compounds into small pieces of materials, put them into a container containing a dispersion solvent, stir them using a high-speed stirrer to fully dissolve them, filter them, and store them in a sealed manner to obtain the ethylene-propylene rubber conductive coating.

[0042] Among them, step S10 is carried out at room temperature for 18-25 min.

[0043] In a preferred embodiment, step S20 specifically includes:

[0044] Step S21: First, add all the tackifier, the first portion of plasticizer, and the second portion of conductive carbon black to the first rubber compound, heat it up to 98 - 105 °C, and knead for 18 - 25 min.

[0045] Step S22: Then, add the remaining portion of plasticizer and the third portion of conductive carbon black, knead with a kneader for 18 - 25 min, and then add the remaining portion of conductive carbon black, and continue to knead in a closed state for 25 - 35 min to obtain the second rubber compound.

[0046] In this embodiment, 80 - 150 parts of plasticizer and 80 - 120 parts of conductive carbon black are added to the first rubber compound in multiple times for kneading and mixing. This makes the tackifier, plasticizer, and conductive carbon black mix more uniformly in the rubber compound. Among them, the first portion of plasticizer can be 30 - 60% of the total added amount of plasticizer, the second portion of conductive carbon black can be 20 - 30% of the total added amount of conductive carbon black, and the third portion of conductive carbon black can be 20 - 30% of the total added amount of conductive carbon black.

[0047] Further, in step S30, add the vulcanizing agent and accelerator at a roll temperature below 40 °C to avoid vulcanization reaction during the preparation process. In step S40, the stirring speed of the high - speed stirrer is 600 - 1200 rpm, and the stirring time is 60 - 120 min; the purpose of filtration is to remove large - particle substances and impurities so as not to affect the uniformity of the coating.

[0048] The present invention will be further described in detail below with reference to specific embodiments. Referring to Table 1, Table 1 shows the raw material compositions of some feasible embodiments of the present invention, and specific descriptions will be made below in combination with Table 1.

[0049] Table 1 Raw material compositions of each embodiment

[0050]

[0051]

[0052] Among them, " / " indicates that this component is not added.

[0053] Example 1

[0054] In this example, an ethylene - propylene rubber conductive coating is prepared. The raw material formula is as shown in Example 1 of Table 1. The specific preparation steps are as follows:

[0055] Use a kneader to knead ethylene - propylene - diene monomer rubber and heat - resistant agent at room temperature for 20 min to obtain the first rubber compound.

[0056] First, add all the tackifiers, the first portion of the plasticizer, and the second portion of the conductive carbon black to the first rubber compound, heat it to 100 °C and knead for 20 min; then add the remaining portion of the plasticizer and the third portion of the conductive carbon black, knead with a kneader for 20 min, and then add the remaining portion of the conductive carbon black and continue to knead tightly for 30 min to obtain the second rubber compound; among them, the first portion of the plasticizer is 50% of the total added amount of the plasticizer, the second portion of the conductive carbon black is 30% of the total added amount of the conductive carbon black, and the third portion of the conductive carbon black is 30% of the total added amount of the conductive carbon black.

[0057] Place the second rubber compound on an open mill with a roll temperature below 40 °C, add the vulcanizing agent and the accelerator, thin-pass and mix evenly, then take off the sheet and cut it into strip-shaped rubber compounds.

[0058] Cut the above strip-shaped rubber compounds into small pieces of materials, put them into a container filled with a dispersion solvent, stir with a high-speed stirrer, the stirring speed of the high-speed stirrer is 1000 rpm, and the stirring time is 100 min to make them fully dissolved, filter and store them tightly to obtain the ethylene-propylene rubber conductive coating.

[0059] The preparation methods of Example 2 to Example 6 are the same as that of Example 1. The present invention also provides a plurality of comparative examples for comparison with the ethylene-propylene rubber conductive coating of the examples of the present invention. Specifically, the raw material compositions of the comparative examples are shown in Table 2 below, and the preparation methods of the comparative examples all refer to Example 1.

[0060] Comparative Example 1

[0061] The difference between Comparative Example 1 and Example 3 is only that: the added amount of the conductive carbon black is 50 parts.

[0062] Comparative Example 2

[0063] The difference between Comparative Example 2 and Example 3 is only that: no heat vulcanization process is carried out after coating.

[0064] Comparative Example 3

[0065] The difference between Comparative Example 3 and Example 3 is only that: the added amount of the plasticizer is 70 parts.

[0066] Comparative Example 4

[0067] The difference between Comparative Example 4 and Example 3 is only that: no tackifier is added.

[0068] Comparative Example 5

[0069] The difference between Comparative Example 5 and Example 3 is only that: no accelerator is added.

[0070] Table 2 Raw material compositions of Comparative Examples 1 - 5

[0071]

[0072] Further, the conductive coatings prepared in Examples 1-6 and Comparative Examples 1-5 were directly coated on the surface of the ethylene-propylene rubber insulating layer with a coating thickness of 1 mm. The specimens corresponding to Examples 1-6, Comparative Example 1, and Comparative Examples 3-4 after coating were placed in an oven and heated at 100 °C for 2 h, while the specimen of Comparative Example 2 was not heated. The test items for the specimens were as follows: 1. The surface resistance performance of the specimens was tested using a multimeter; 2. The cross-cut test of the paint film was carried out according to the test method of GB / T 9286-1998 to compare the adhesion. The specific test results are shown in Table 3 below.

[0073] Table 3 Test data of Examples 1 to 6 and Comparative Examples 1 to 5

[0074]

[0075] Based on the test data shown in Table 3, the surface resistance of Examples 1-6 was less than 5000 Ω. Among them, compared with Example 3, the addition amount of conductive carbon black in Comparative Example 1 was only 50 parts, and the surface resistance of the obtained conductive coating product increased significantly, indicating that the more the amount of conductive carbon black used within a certain range, the better the conductivity and shielding effect of the ethylene-propylene rubber conductive coating.

[0076] Moreover, based on the test data shown in Table 3, the adhesion of Examples 1-6 was significantly better than that of Comparative Examples 2-5. Compared with Example 3, Comparative Example 2 was not vulcanized, and its adhesion was extremely poor; 70 parts of plasticizer were added in Comparative Example 3, which was not within the component range of this application, and the adhesion of the obtained conductive coating product was also slightly poor, with poor bonding performance; compared with Example 3, no tackifier was added in Comparative Example 4, and the adhesion of the obtained conductive coating product was poor, indicating poor bonding performance; further indicating that the tackifier and plasticizer in the components of this application have a synergistic effect, and the simultaneous addition makes the bonding performance of the ethylene-propylene rubber conductive coating stronger; compared with Example 3, no vulcanization accelerator was added in Comparative Example 5, the vulcanization degree of the coating was not high, and the adhesion of the obtained conductive coating product was poor, indicating poor bonding performance.

[0077] In addition, the present invention also provides a cable accessory, including an insulating layer and a coating layer coated on the outer surface of the insulating layer. Specifically, the coating layer is formed by spraying or brushing the aforementioned ethylene-propylene rubber conductive coating, and a heat vulcanization process is carried out after coating. The thickness of the coating layer is 0.5-1 mm. The present invention uses the ethylene-propylene rubber conductive coating to coat the outside of the insulating layer to replace the existing conductive shielding layer that needs to be prefabricated in a mold, which plays an outer shielding or conductive role. Compared with the mold forming process, it has the advantages of saving molds and equipment, simple operation, and low cost.

[0078] It should be noted that in this document, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or system comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or system. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or system comprising such element.

[0079] The serial numbers of the embodiments of the present invention above are for description only and do not represent the superiority or inferiority of the embodiments.

[0080] The above are only the preferred embodiments of the present invention and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are similarly included in the patent protection scope of the present invention.

Claims

1. An ethylene-propylene rubber conductive coating, characterized in that, the ethylene-propylene rubber conductive coating is not vulcanized during the preparation process and is heated and vulcanized after coating. The ethylene-propylene rubber conductive coating comprises the following preparation raw materials by mass parts: 100 parts of ethylene-propylene rubber, 1-3 parts of heat-resistant agent, 80-150 parts of plasticizer, 5-20 parts of tackifier, 80-120 parts of conductive carbon black, 1-3 parts of vulcanizing agent, 2-4 parts of accelerator, and 150-300 parts of dispersion solvent.

2. The ethylene-propylene rubber conductive coating according to claim 1, characterized in that, the heat-resistant agent is nano-sized zinc oxide, the plasticizer is one or more of white naphthenic oil, transformer oil, and paraffin oil, and the tackifier is one or more of phenolic resin, petroleum resin, and coumarone resin; the dispersion solvent is one or more of toluene, xylene, and acetone.

3. The ethylene-propylene rubber conductive coating according to claim 1, characterized in that, the dispersion solvent is a mixture of toluene, xylene, and acetone according to the mass parts of 1:2:

1.

4. The ethylene-propylene rubber conductive coating according to claim 1, characterized in that, the accelerator is one or more of thiuram accelerators, thiazole accelerators, and sulfenamide accelerators.

5. The ethylene-propylene rubber conductive coating according to claim 1, characterized in that, the vulcanizing agent is sulfur; the temperature of the heat-vulcanization process is 80-150 °C, and the heating time is 1-2 h.

6. A preparation method of an ethylene-propylene rubber conductive coating, characterized in that, the preparation method of the ethylene-propylene rubber conductive coating is used to prepare the ethylene-propylene rubber conductive coating according to any one of claims 1 to 5. The preparation method of the ethylene-propylene rubber conductive coating comprises the following steps: Kneading ethylene-propylene rubber and a heat-resistant agent by a kneader to obtain a first rubber compound; Adding a tackifier, a plasticizer, and conductive carbon black to the first rubber compound, and kneading and mixing by a kneader to obtain a second rubber compound; Placing the second rubber compound on an open mill with a roll temperature below 40 °C, adding a vulcanizing agent and an accelerator, thinly passing and mixing evenly, then taking off the sheet and cutting it into strip-shaped rubber compounds; Cutting the above strip-shaped rubber compounds into small pieces of materials, putting them into a container containing a dispersion solvent, stirring by a high-speed stirrer to make them fully dissolved, filtering, and storing them in a sealed manner to obtain the ethylene-propylene rubber conductive coating.

7. The preparation method of the ethylene-propylene rubber conductive coating according to claim 6, characterized in that, the stirring speed of the high-speed stirrer is 600-1200 rpm, and the stirring time is 60-120 min.

8. The preparation method of the ethylene-propylene rubber conductive coating according to claim 6, characterized in that, the step of adding a tackifier, a plasticizer, and conductive carbon black to the first rubber compound and kneading and mixing by a kneader to obtain a second rubber compound comprises: First, adding all the tackifier, the first portion of the plasticizer, and the second portion of the conductive carbon black to the first rubber compound, heating to 98-105 °C, and kneading for 18-25 min; Add the remaining amount of plasticizer and the third amount of conductive carbon black, knead with a kneader for 18 - 25 min, then add the remaining amount of conductive carbon black, and continue to knead in a closed state for 25 - 35 min to obtain the second rubber compound.

9. A cable accessory, characterized in that, the cable accessory includes an insulating layer and a coating layer coated on the outer surface of the insulating layer, and the coating layer is formed by spraying or brushing with the ethylene - propylene rubber conductive coating according to any one of claims 1 to 5.

10. The cable accessory according to claim 9, characterized in that, the thickness of the coating layer is 0.5 - 1 mm.

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